Film etching method for etching film

ABSTRACT

An etching method includes a step of selectively forming deposit on a top surface of a mask disposed on a film of a substrate, a step of etching the film after the step of forming the deposit, a step of forming a layer of chemical species included in plasma of a processing gas, on the substrate, and a step of supplying ions from plasma of an inert gas to the substrate so that the chemical species react with the film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority from Japanese PatentApplication No. 2019-007137, filed on Jan. 18, 2019 with the JapanPatent Office, the disclosure of which is incorporated herein in itsentirety by reference.

TECHNICAL FIELD

The present disclosure relates to a film etching method.

BACKGROUND

In manufacturing electronic devices, a film on a substrate is etched. Amask is placed on the film of the substrate for an etching process and apattern of the mask is transferred to the film by the etching. Theetching may be performed by using a plasma processing apparatus asdescribed in, for example, Japanese Patent Laid-Open Publication No.2015-173240 or No. 2018-098480.

SUMMARY

In an embodiment, a method of etching a film of a substrate is provided.The method includes a step of providing the substrate that has the filmand a mask on the film. The method further includes a step ofselectively forming a deposit on a top surface of the mask. The methodfurther includes a step of etching the film after the step of formingthe deposit. The etching step includes a step of forming, on thesubstrate, a layer of chemical species included in plasma of aprocessing gas. The etching step further includes a step of supplyingions from plasma of an inert gas to the substrate, thereby causing thechemical species and the film to react with each other.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the accompanying drawings and thefollowing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of a method according to an embodiment.

FIG. 2 is a sectional view of a part of a substrate as an example, in anenlarged scale.

FIG. 3 is a view schematically illustrating a plasma processingapparatus as an example that may be used for executing the methodillustrated in FIG. 1.

FIG. 4A, FIG. 4B, FIG. 4C, and FIG. 4D are sectional views of a part ofthe substrate as an example, in an enlarged scale, in a state after theexecution of step ST1, a state after the execution of step ST21, a stateafter the execution of step ST22, and a state after the execution of themethod MT, respectively.

FIG. 5 is a flow chart of the step ST1 in the method according to theembodiment.

FIG. 6 is a timing chart as an example related to the step ST1illustrated in FIG. 5.

FIG. 7 is a flow chart of step ST2 in an example.

FIG. 8 is a flow chart of the step ST2 in another example.

FIG. 9A, FIG. 9B, FIG. 9C, and FIG. 9D are sectional views of a part ofthe substrate as an example, in an enlarged scale, in a state after theexecution of the step ST1, a state after the execution of step ST25, astate after the execution of step ST26, and a state after the executionof the method MT, respectively.

FIG. 10 is a graph illustrating a calculation result of the depth fromthe surface, which is reached by hydrogen ions within a film.

FIG. 11 is a view schematically illustrating a processing system as anexample which may be used for executing the method illustrated in FIG.1.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part thereof. The illustrativeembodiments described in the detailed description, drawings, and claimsare not meant to be limiting. Other embodiments may be utilized, andother changes may be made without departing from the spirit or scope ofthe subject matter presented here.

Hereinafter, various embodiments will be described.

In an embodiment, a method of etching a film of a substrate is provided.The method includes a step of preparing the substrate that has the filmand a mask on the film. The method further includes a step ofselectively forming a deposit on a top surface of the mask. The methodfurther includes a step of etching the film after the step of formingthe deposit. The etching step includes a step of forming, on thesubstrate, a layer of chemical species included in plasma of aprocessing gas. The etching step further includes a step of supplyingions from plasma of an inert gas to the substrate, thereby causing thechemical species and the film to react with each other. According tothis embodiment, due to the deposit selectively formed on the topsurface of the mask, the mask is protected during etching of the film.Therefore, the film thickness of the mask is suppressed from beingdecreased due to etching of the film. Since the deposit is selectivelyformed on the top surface of the mask, the etching efficiency of thefilm is suppressed from being lowered due to the deposit.

In the embodiment, the film of the substrate may be a silicon-containingfilm. The processing gas may contain a halogen element and carbon. Inthe embodiment, the inert gas may contain a rare gas.

In another embodiment, a method of etching a film of a substrate isprovided. The method includes a step of preparing the substrate that hasthe film and a mask on the film. The method includes a step ofselectively forming a deposit on a top surface of the mask. The methodincludes a step of etching the film after the step of forming thedeposit. The etching step includes a step of modifying at least a partof the film that includes an exposed surface of the film by ions fromplasma of a first processing gas. In the modifying step, a modifiedregion is formed from the at least a part of the film. The etching stepfurther includes a step of selectively etching the modified region bychemical species from plasma of a second processing gas. According tothis embodiment, due to the deposit selectively formed on the topsurface of the mask, the mask is protected during etching of the film.Therefore, the film thickness of the mask is suppressed from beingdecreased due to etching of the film. Since the deposit is selectivelyformed on the top surface of the mask, the etching efficiency of thefilm is suppressed from being lowered due to the deposit.

In the embodiment, the film of the substrate may be a silicon nitridefilm. In this embodiment, the first processing gas may contain ahydrogen-containing gas, and the second processing gas may contain afluorine-containing gas and a hydrogen gas.

In the embodiment, the film of the substrate may be a silicon carbidefilm. In this embodiment, the first processing gas may contain anitrogen-containing gas, and the second processing gas may contain afluorine-containing gas and a hydrogen gas.

In the embodiment, a thickness of the deposit may be set such that theions from the plasma of the first processing gas do not reach the maskby passing through the deposit.

In the embodiment, the step of forming the deposit may be performed in astate where the substrate is accommodated within a chamber of a plasmaprocessing apparatus. In the step of forming the deposit, plasma of amixed gas containing a hydrocarbon gas and an adjusting gas that adjustsan amount of the deposit may be formed within the chamber. In thisembodiment, the deposit containing carbon included in the plasma of themixed gas may be formed on the top surface of the mask.

In the embodiment, the step of forming the deposit may be performed in astate where the substrate is accommodated within a chamber of a plasmaprocessing apparatus. The step of forming the deposit may include a stepof supplying a mixed gas containing a silicon-containing gas and anadjusting gas that adjusts an amount of the deposit into the chamber.The step of forming the deposit may further include a step of supplyingthe adjusting gas into the chamber. The step of supplying the mixed gasand the step of supplying the adjusting gas may be alternately repeated.A radio-frequency power may be supplied in order to generate plasma fromthe mixed gas within the chamber during execution of the step ofsupplying the mixed gas, and to generate plasma from the adjusting gaswithin the chamber during execution of the step of supplying theadjusting gas.

In the embodiment, the plasma processing apparatus includes the chamber,a substrate holder, an upper electrode, a first radio-frequency powersupply, and a second radio-frequency power supply. The substrate holderincludes a lower electrode and is configured to support the substratewithin the chamber. The upper electrode is provided above the substrateholder through a space within the chamber. The first radio-frequencypower supply is electrically connected to the upper electrode and isconfigured to generate a first radio-frequency power. The secondradio-frequency power supply is electrically connected to the lowerelectrode and is configured to generate a second radio-frequency powerhaving a frequency lower than a frequency of the first radio-frequencypower.

Hereinafter, various embodiments will be described in detail withreference to drawings. In the drawings, the same or correspondingportions are denoted by the same reference numerals.

FIG. 1 is a flow chart of a method according to an embodiment. A methodMT illustrated in FIG. 1 is executed for etching a film of a substrate.The method MT may include step STa. In the step STa, the substrate isprepared. FIG. 2 is a sectional view of a part of the substrate as anexample, in an enlarged scale. The method MT may be applied to asubstrate W as an example illustrated in FIG. 2. The substrate Wincludes a film EF and a mask MK. The substrate W may further include abase region UR. The film EF is provided on the base region UR. The filmEF may be a silicon-containing film. The film EF may be, for example, asilicon oxide film, a silicon nitride film, or a silicon carbide film.

The mask MK is provided on the film EF. The mask MK is patterned. Thatis, the mask MK provides one or more openings. The mask MK is made of amaterial different from the material of the film EF. The mask MK may beformed of a silicon-containing film, an organic film or ametal-containing film. The silicon-containing film may be made ofsilicon, silicon oxide or silicon nitride. The organic film may be madeof amorphous carbon or a photoresist material. The metal-containing filmmay be made of titanium, tantalum, tungsten, or a nitride or an oxide ofany of these metals.

In the embodiment, an opening continuous from the opening of the mask MKmay be formed in the film EF. The opening of the film EF may be formedthrough, for example, plasma etching.

In the embodiment, a single plasma processing apparatus may be used forexecuting the method MT. FIG. 3 is a view schematically illustrating aplasma processing apparatus as an example that may be used for executingthe method illustrated in FIG. 1. A plasma processing apparatus 1illustrated in FIG. 3 is a capacitively coupled plasma processingapparatus. The plasma processing apparatus 1 includes a chamber 10. Thechamber 10 provides an internal space 10 s therein.

The chamber 10 includes a chamber body 12. The chamber body 12 has asubstantially cylindrical shape. The internal space 10 s is providedinside the chamber body 12. The chamber body 12 is made of conductorsuch as aluminum. The chamber body 12 is grounded. A corrosion resistantfilm is formed on the inner wall surface of the chamber body 12. Thecorrosion resistant film may be a film made of ceramic such as aluminumoxide or yttrium oxide.

A passage 12 p is formed in a side wall of the chamber body 12. Thesubstrate W passes through the passage 12 p when transferred between theinternal space 10 s and the outside of the chamber 10. The passage 12 pis configured to be opened or closed by a gate valve 12 g. The gatevalve 12 g is provided along the side wall of the chamber body 12.

A support 13 is provided on the bottom of the chamber body 12. Thesupport 13 is made of an insulating material. The support 13 has asubstantially cylindrical shape. The support 13 extends upwards from thebottom of the chamber body 12 within the internal space 10 s. Thesupport 13 supports a substrate holder 14. The substrate holder 14 isconfigured to support the substrate W within the chamber 10, that is,within the internal space 10 s.

The substrate holder 14 has a lower electrode 18 and an electrostaticchuck 20. The lower electrode 18 and the electrostatic chuck 20 areprovided within the chamber 10. The substrate holder 14 may furtherinclude an electrode plate 16. The electrode plate 16 is made of, forexample, conductor such as aluminum, and has substantially a disc shape.The lower electrode 18 is provided on the electrode plate 16. The lowerelectrode 18 is made of, for example, conductor such as aluminum, andhas substantially a disc shape. The lower electrode 18 is electricallyconnected to the electrode plate 16.

The electrostatic chuck 20 is provided on the lower electrode 18. Thesubstrate W is placed on the top surface of the electrostatic chuck 20.The electrostatic chuck 20 has a main body and an electrode. The mainbody of the electrostatic chuck 20 is made of dielectric. The electrodeof the electrostatic chuck 20 is a film-shaped electrode and is providedwithin the main body of the electrostatic chuck 20. The electrode of theelectrostatic chuck 20 is connected to a DC power supply 20 p via aswitch 20 s. When a voltage is applied from the DC power supply 20 p tothe electrode of the electrostatic chuck 20, electrostatic attraction isgenerated between the electrostatic chuck 20 and the substrate W. Due tothe generated electrostatic attraction, the substrate W is attracted tothe electrostatic chuck 20 and is held by the electrostatic chuck 20.

A focus ring FR is disposed on the substrate holder 14. The focus ringFR may be made of silicon, silicon carbide, or quartz, but the presentdisclosure is not limited thereto. When the substrate W is processedwithin the chamber 10, the substrate W is disposed on the electrostaticchuck 20 within a region surrounded by the focus ring FR.

A flow path 18 f is provided inside the lower electrode 18. A heatexchange medium (for example, coolant) is supplied to the flow path 18 fthrough a pipe 22 a from a chiller unit 22. The chiller unit 22 isprovided outside the chamber 10. The heat exchange medium supplied tothe flow path 18 f is returned to the chiller unit 22 through a pipe 22b. In the plasma processing apparatus 1, the temperature of thesubstrate W placed on the electrostatic chuck 20 is adjusted by heatexchange between the heat exchange medium and the lower electrode 18.

The plasma processing apparatus 1 may further include a gas supply line24. The gas supply line 24 supplies a heat transfer gas (for example, Hegas) to a gap between the top surface of the electrostatic chuck 20 andthe back surface of the substrate W. The heat transfer gas is suppliedfrom a heat transfer gas supply mechanism to the gas supply line 24.

The plasma processing apparatus 1 further includes an upper electrode30. The upper electrode 30 is provided above the substrate holder 14.The upper electrode 30 is supported on the upper portion of the chamberbody 12 via a member 32. The member 32 is made of an insulatingmaterial. The upper electrode 30 and the member 32 close an upperopening of the chamber body 12.

The upper electrode 30 may include a top plate 34 and a support 36. Thebottom surface of the top plate 34 is a bottom surface on the internalspace 10 s side, and defines the internal space 10 s. The top plate 34is made of a silicon-containing material. The top plate 34 is made of,for example, silicon or silicon carbide. A plurality of gas dischargeholes 34 a is formed in the top plate 34. The gas discharge holes 34 apass through the top plate 34 in the plate thickness direction.

The support 36 detachably supports the top plate 34. The support 36 ismade of a conductive material such as aluminum. A gas diffusion chamber36 a is provided inside the support 36. A plurality of gas holes 36 b isformed in the support 36. The gas holes 36 b extend downwards from thegas diffusion chamber 36 a. The gas holes 36 b communicate with the gasdischarge holes 34 a, respectively. A gas introducing port 36 c isformed in the support 36. The gas introducing port 36 c is connected tothe gas diffusion chamber 36 a. A gas supply pipe 38 is connected to thegas introducing port 36 c.

A gas source group 40 is connected to the gas supply pipe 38 via a valvegroup 41, a flow rate controller group 42 and a valve group 43. The gassource group 40, the valve group 41, the flow rate controller group 42,and the valve group 43 constitute a gas supply GS. The gas source group40 includes a plurality of gas sources. The plurality of gas sources inthe gas source group 40 includes sources of a plurality of gases used inthe method MT. Each of the valve group 41 and the valve group 43includes a plurality of open/close valves. The flow rate controllergroup 42 includes a plurality of flow rate controllers. Each of the flowrate controllers in the flow rate controller group 42 is a mass flowcontroller or a pressure control-type flow rate controller. Each of thegas sources in the gas source group 40 is connected to the gas supplypipe 38 through the corresponding open/close valve of the valve group41, the corresponding flow rate controller of the flow rate controllergroup 42, and the corresponding open/close valve of the valve group 43.

In the plasma processing apparatus 1, a shield 46 is detachably providedalong the inner wall surface of the chamber body 12. The shield 46 isalso provided on the outer periphery of the support 13. The shield 46prevents a by-product of plasma processing from adhering to the chamberbody 12. The shield 46 is configured by forming a corrosion resistantfilm on the surface of a member made of, for example, aluminum. Thecorrosion resistant film may be a film made of ceramic such as yttriumoxide.

A baffle plate 48 is provided between the support 13 and the side wallof the chamber body 12. The baffle plate 48 is configured by forming acorrosion resistant film on the surface of a member made of, forexample, aluminum. The corrosion resistant film may be a film made ofceramic such as yttrium oxide. A plurality of through holes is formed inthe baffle plate 48. An exhaust port 12 e is provided below the baffleplate 48 at the bottom of the chamber body 12. An exhaust device 50 isconnected to the exhaust port 12 e via an exhaust pipe 52. The exhaustdevice 50 includes a pressure adjusting valve and a vacuum pump such asa turbo molecular pump.

The plasma processing apparatus 1 further includes a firstradio-frequency power supply 62 and a second radio-frequency powersupply 64. The first radio-frequency power supply 62 is a power supplythat generates a first radio-frequency power. As an example, the firstradio-frequency power has a frequency suitable for generating plasma.The frequency of the first radio-frequency power is a frequency rangingfrom, for example, 27 MHz to 100 MHz. As an example, the frequency ofthe first radio-frequency power may be 60 MHz. The first radio-frequencypower supply 62 is connected to the upper electrode 30 via a matchingunit 66. The matching unit 66 has a circuit that matches the outputimpedance of the first radio-frequency power supply 62 to the load-side(the upper electrode 30 side) impedance. Further, the firstradio-frequency power supply 62 may be connected to the lower electrode18 via the matching unit 66.

The second radio-frequency power supply 64 is a power supply thatgenerates a second radio-frequency power. The second radio-frequencypower has a frequency lower than the frequency of the firstradio-frequency power. The second radio-frequency power may be used as abias radio-frequency power for drawing ions to the substrate W. Thefrequency of the second radio-frequency power is a frequency rangingfrom, for example, 400 kHz to 40 MHz. As an example, the frequency ofthe second radio-frequency power may be 40 MHz. The secondradio-frequency power supply 64 is connected to the lower electrode 18via a matching unit 68 and the electrode plate 16. The matching unit 68has a circuit that matches the output impedance of the secondradio-frequency power supply 64 to the load-side (the lower electrode 18side) impedance. Further, the plasma processing apparatus 1 may includeany one of the first radio-frequency power supply 62 and the secondradio-frequency power supply 64.

The plasma processing apparatus 1 further includes a controller MC. Thecontroller MC may be a computer that includes, for example, a processor,a storage unit such as a memory, an input device, a display device, andan input/output interface for signals. The controller MC controls eachunit of the plasma processing apparatus 1. In the controller MC, anoperator may perform, for example, a command input operation by usingthe input device in order to manage the plasma processing apparatus 1.In the controller MC, an operating status of the plasma processingapparatus 1 may be visually displayed by the display device. The storageunit of the controller MC stores a control program and recipe data. Thecontrol program is executed by the processor of the controller MC suchthat various processings may be performed in the plasma processingapparatus 1. When the processor of the controller MC executes thecontrol program, and controls each unit of the plasma processingapparatus 1 according to the recipe data, the method MT is performed inthe plasma processing apparatus 1.

Referring back to FIG. 1, the method MT will be described in detail. Inthe following description, the method MT will be described by using acase where the method MT is applied to the substrate W by using theplasma processing apparatus 1, as an example. In the followingdescription, reference is made to FIG. 4A, FIG. 4B, FIG. 4C, and FIG. 4Das well as FIG. 1. FIG. 4A, FIG. 4B, FIG. 4C, and FIG. 4D are sectionalviews of a part of the substrate as an example, in an enlarged scale, ina state after the execution of step ST1, a state after the execution ofstep ST21, a state after the execution of step ST22, and a state afterthe execution of the method MT, respectively.

As illustrated in FIG. 1, the method MT includes the step ST1 and thestep ST2. In the embodiment, the method MT is performed in a state wherethe substrate W is held by the electrostatic chuck 20 within the chamber10.

In the step ST1, as illustrated in FIG. 4A, a deposit DP is selectivelyformed on a top surface TS of the mask MK. In the step ST1, formation ofthe deposit on the side surface of the mask MK and the surface of thefilm EF exposed from the mask MK is substantially suppressed. Forexample, in the step ST1, when the aspect ratio of an opening is 1 ormore, the deposit is not formed on the surface of the film EF (thesurface of the film EF that defines the bottom of the opening). Here,the opening is an opening continuous from an opening of the mask MK orthe mask MK to the inside of the film EF. As an example, (the thicknessof the deposit DP)/(the width of the opening) may be 1 or more and 2 orless. In the step ST1, the deposit DP may be formed by a plasmaprocessing using a raw material gas. In the embodiment, the deposit DPmay be formed by a plasma processing using a mixed gas containing a rawmaterial gas.

In the step ST1 in the embodiment, as for the raw material gas, acarbon-containing gas, for example, a hydrocarbon gas is used. In thestep ST1 in the embodiment, plasma of a mixed gas containing thecarbon-containing gas and an adjusting gas is formed within the chamber10. The hydrocarbon gas is, for example, CH₄ gas. The adjusting gas is agas that adjusts the amount of the deposit DP. As an example, theadjusting gas is a nitrogen-containing gas. The nitrogen-containing gasis, for example, a nitrogen gas (N₂ gas) or NH₃ gas. In this embodiment,carbon-containing chemical species included in the plasma of the mixedgas are selectively deposited on the top surface TS of the mask MK toform the deposit DP.

In the step ST1 in another embodiment, as for the raw material gas, asilicon-containing gas is used. In the step ST1 in the embodiment,plasma of a mixed gas containing the silicon-containing gas and anadjusting gas is formed within the chamber 10. The silicon-containinggas is, for example, an aminosilane gas. The adjusting gas is a gas thatadjusts the thickness of the deposit DP to be formed. The adjusting gascontains a rare gas or a nitrogen-containing gas. The rare gas is, forexample, an argon gas or a helium gas. The nitrogen-containing gas is,for example, a nitrogen gas (N₂ gas) or NH₃ gas. The adjusting gas mayfurther contain a halogen-based gas (a gas containing a halogenelement). In this embodiment, silicon-containing chemical speciesincluded in the plasma of the mixed gas are selectively deposited on thetop surface TS of the mask MK to form the deposit DP. In the step ST1 inthis embodiment, the deposit DP may contain, for example, silicon,oxygen, and carbon. The deposit DP are made of, for example, SiOC. Inthis embodiment, the film EF is, for example, a silicon nitride film ora silicon carbide film.

In order to execute the step ST1, the controller MC controls the gassupply GS to supply the mixed gas into the chamber 10. The controller MCcontrols the exhaust device 50 to set the pressure within the chamber 10to a predetermined pressure. The controller MC controls the firstradio-frequency power supply 62 and/or the second radio-frequency powersupply 64 to supply the first radio-frequency power and/or the secondradio-frequency power. In the step ST1, only the second radio-frequencypower out of the first radio-frequency power and the secondradio-frequency power may be supplied.

Hereinafter, reference is made to FIG. 5 and FIG. 6. FIG. 5 is a flowchart of the step ST1 in the method according to the embodiment. FIG. 6is a timing chart as an example related to the step ST1 illustrated inFIG. 5. In FIG. 6, the horizontal axis indicates time. In FIG. 6, thevertical axis indicates a radio-frequency power, a flow rate of asilicon-containing gas, and a flow rate of an adjusting gas.

In the step ST1 in the embodiment, step ST11 and step ST12 arealternately repeated. In the step ST1, step ST13 is executed so as todetermine whether a stop condition is satisfied. The stop condition issatisfied when the number of repetitions of the step ST11 and the stepST12 reaches a predetermined number of times. In the step ST13, when itis determined that the stop condition is not satisfied, the step ST11and the step ST12 are executed again. Meanwhile, in the step ST13, whenit is determined that the stop condition is satisfied, the step ST1 isended.

In the step ST11, a mixed gas is supplied into the chamber 10. The mixedgas contains a silicon-containing gas and an adjusting gas. In the stepST12, the adjusting gas is supplied into the chamber 10. Duringexecution of the step ST12, supplying of the silicon-containing gas intothe chamber 10 is stopped. The silicon-containing gas is, for example,an aminosilane gas. The adjusting gas is a gas that adjusts thethickness of the deposit DP to be formed. The adjusting gas contains arare gas or a nitrogen-containing gas. The rare gas is, for example, anargon gas or a helium gas. The nitrogen-containing gas is, for example,a nitrogen gas (N₂ gas) or NH₃ gas. The adjusting gas may furthercontain a halogen-based gas (a gas containing a halogen element). Duringexecution of the step ST11, plasma of the mixed gas is generated withinthe chamber 10. In the step ST11, chemical species generated bydissociation of the silicon-containing gas are deposited on the topsurface TS of the mask MK. During execution of the step ST12, plasma ofthe adjusting gas is generated within the chamber 10. In the step ST12,the chemical species extending on the top surface TS of the mask MKreact with ions from the plasma of the adjusting gas (for example, thenitrogen-containing gas). As a result, the deposit DP are formed.

The power level of the radio-frequency power in the step ST11 may belower than the power level of the radio-frequency power in the stepST12. In the step ST11 and the step ST12, both or one of the firstradio-frequency power and the second radio-frequency power are/is usedas the radio-frequency power. In the embodiment, only the firstradio-frequency power is used as the radio-frequency power. The powerlevel of the radio-frequency power in the step ST11 may be substantiallyequal to the power level of the radio-frequency power in the step ST12.

In order to execute the step ST11, the controller MC controls the gassupply GS to supply the mixed gas into the chamber 10. In order toexecute the step ST11, the controller MC controls the exhaust device 50to set the pressure within the chamber 10 to a predetermined pressure.In order to execute the step ST11, the controller MC controls the firstradio-frequency power supply 62 and/or the second radio-frequency powersupply 64 to supply the first radio-frequency power and/or the secondradio-frequency power.

In order to execute the step ST12, the controller MC controls the gassupply GS to supply the adjusting gas into the chamber 10. In order toexecute the step ST12, the controller MC controls the exhaust device 50to set the pressure within the chamber 10 to a predetermined pressure.In order to execute the step ST12, the controller MC controls the firstradio-frequency power supply 62 and/or the second radio-frequency powersupply 64 to supply the first radio-frequency power and/or the secondradio-frequency power.

Referring back to FIG. 1, in the method MT, subsequently, the step ST2is executed. In step ST2, the film EF is etched. FIG. 7 is a flow chartof the step ST2 in an example. As illustrated in FIG. 7, in theembodiment, the step ST2 includes the step ST21 and the step ST22.

In the step ST2, the step ST21 and the step ST22 may be alternatelyrepeated. In this case, in the step ST2, step ST23 is executed so as todetermine whether a stop condition is satisfied. The stop condition issatisfied when the number of repetitions of the step ST21 and the stepST22 reaches a predetermined number of times. In the step ST23, when itis determined that the stop condition is not satisfied, the step ST21and the step ST22 are executed again. Meanwhile, in the step ST23, whenit is determined that the stop condition is satisfied, the step ST2 isended.

In the step ST21, a layer CL of chemical species included in plasma of aprocessing gas is formed on the substrate W (see FIG. 4B). In theembodiment, the film EF is a silicon-containing film. The film EF is,for example, a silicon oxide film. In this embodiment, the processinggas used in the step ST21 contains a halogen element and carbon. Theprocessing gas contains, for example, a fluorocarbon gas. The processinggas may contain an oxygen-containing gas and/or a rare gas. In the stepST21, chemical species (for example, fluorocarbon) from the plasma ofthe processing gas are deposited on the substrate W to form the layerCL.

In the step ST22, ions are supplied from plasma of an inert gas to thesubstrate W so that the chemical species within the layer CL react witha constituent material of the film EF. The inert gas may be a rare gassuch as an argon gas. When ions are supplied from the plasma of theinert gas to the layer CL, a reaction between the chemical specieswithin the layer CL and the constituent material of the film EF isfacilitated, and a reaction product is exhausted. As a result, the filmEF is etched (see FIG. 4C).

In order to execute the step ST21, the controller MC controls the gassupply GS to supply the processing gas into the chamber 10. In order toexecute the step ST21, the controller MC controls the exhaust device 50to set the pressure within the chamber 10 to a predetermined pressure.In order to execute the step ST21, the controller MC controls the firstradio-frequency power supply 62 and/or the second radio-frequency powersupply 64 to supply the first radio-frequency power and/or the secondradio-frequency power.

In order to execute the step ST22, the controller MC controls the gassupply GS to supply the inert gas into the chamber 10. In order toexecute the step ST22, the controller MC controls the exhaust device 50to set the pressure within the chamber 10 to a predetermined pressure.In order to execute the step ST22, the controller MC controls the firstradio-frequency power supply 62 and/or the second radio-frequency powersupply 64 to supply the first radio-frequency power and/or the secondradio-frequency power.

As illustrated in FIG. 1, the step ST1 and the step ST2 may bealternately repeated. In this case, the method MT further includes stepST3 as illustrated in FIG. 1. In the step ST3, it is determined whethera stop condition is satisfied. The stop condition is satisfied when thenumber of repetitions of the step ST1 and the step ST2 reaches apredetermined number of times. In the step ST3, when it is determinedthat the stop condition is not satisfied, the step ST1 and the step ST2are executed again. Meanwhile, in the step ST3, when it is determinedthat the stop condition is satisfied, the method MT is ended. When themethod MT is ended, as illustrated in FIG. 4D, the film EF may be placedin a state where etching has been performed until the base region UR isexposed.

According to the method MT, due to the deposit DP selectively formed onthe top surface TS of the mask MK, the mask MK is protected duringetching of the film EF. Therefore, the film thickness of the mask MK issuppressed from being decreased due to etching of the film EF. Since thedeposit DP are selectively formed on the top surface TS of the mask MK,the etching efficiency of the film EF is suppressed from being lowereddue to the deposit DP.

Hereinafter, reference is made to FIG. 8, FIG. 9A, FIG. 9B, FIG. 9C, andFIG. 9D. FIG. 8 is a flow chart of the step ST2 in another example. FIG.9A, FIG. 9B, FIG. 9C, and FIG. 9D are sectional views of a part of thesubstrate as an example, in an enlarged scale, in a state after theexecution of the step ST1, a state after the execution of step ST25, astate after the execution of step ST26, and a state after the executionof the method MT, respectively.

In another embodiment, the step ST2 of the method MT may include thestep ST25 and the step ST26 as illustrated in FIG. 8. The step ST25 andthe step ST26 may be alternately repeated. In this case, in the stepST2, step ST27 is executed so as to determine whether a stop conditionis satisfied. The stop condition is satisfied when the number ofrepetitions of the step ST25 and the step ST26 reaches a predeterminednumber of times. In the step ST27, when it is determined that the stopcondition is not satisfied, the step ST25 and the step ST26 are executedagain. Meanwhile, in the step ST27, when it is determined that the stopcondition is satisfied, the step ST2 is ended.

In the method MT including the step ST2 illustrated in FIG. 8, the filmEF may be a silicon nitride film or a silicon carbide film. In themethod MT including the step ST2 illustrated in FIG. 8, the deposit DPis also similarly formed on the film EF in the step ST1 (see FIG. 9A).

In the step ST25, at least a part of the film EF is modified by ionsfrom plasma of a first processing gas. At least a part of the film EFincludes an exposed surface of the film EF. Through the step ST25, amodified region MR is formed from at least a part of the film EF (seeFIG. 9B).

When the film EF is a silicon nitride film, the first processing gas maycontain a hydrogen-containing gas. The hydrogen-containing gas is, forexample, a hydrogen gas (H₂ gas). When the film EF is a silicon carbidefilm, the first processing gas may contain a nitrogen-containing gas.The nitrogen-containing gas is, for example, a nitrogen gas (N₂ gas) orNH₃ gas. In the step ST25, in order to cause ions to enter the inside ofthe film EF, the second radio-frequency power as well as the firstradio-frequency power is used, and the ions are drawn to the film EF.

In the step ST26, the modified region MR is selectively etched bychemical species from plasma of a second processing gas. When the filmEF is the silicon nitride film and when the film EF is the siliconcarbide film, the second processing gas contains a fluorine-containinggas and a hydrogen gas (H₂ gas). The fluorine-containing gas is, forexample, NF₃ gas. Another fluorine-containing gas may be used. Due tothe chemical species from the plasma of the second processing gas,etching of the deposit DP is suppressed, and the modified region MR isselectively etched.

In order to execute the step ST25, the controller MC controls the gassupply GS to supply the first processing gas into the chamber 10. Inorder to execute the step ST25, the controller MC controls the exhaustdevice 50 to set the pressure within the chamber 10 to a predeterminedpressure. In order to execute the step ST25, the controller MC controlsthe first radio-frequency power supply 62 and the second radio-frequencypower supply 64 to supply the first radio-frequency power and the secondradio-frequency power.

In order to execute the step ST26, the controller MC controls the gassupply GS to supply the second processing gas into the chamber 10. Inorder to execute the step ST26, the controller MC controls the exhaustdevice 50 to set the pressure within the chamber 10 to a predeterminedpressure. In order to execute the step ST26, the controller MC controlsthe first radio-frequency power supply 62 and/or the secondradio-frequency power supply 64 to supply the first radio-frequencypower and/or the second radio-frequency power.

When this method MT is ended, as illustrated in FIG. 9D, the film EF maybe placed in a state where etching has been performed until the baseregion UR is exposed.

In the step ST1 in the embodiment, the thickness of the deposit DP maybe set such that the ions from the plasma of the first processing gas donot reach the mask MK through the deposit DP. The thickness of thedeposit DP may be controlled by adjusting the processing time of thestep ST1 and/or the power level of the radio-frequency power used in thestep ST1. Here, reference is made to FIG. 10. FIG. 10 is a graphillustrating a calculation result of the depth from the surface, whichis reached by hydrogen ions within a film. In FIG. 10, the horizontalaxis indicates the depth from the surface, which is reached by thehydrogen ions within the film, and the vertical axis indicates theconcentration of the hydrogen ions. As illustrated in FIG. 10, as theenergy of the hydrogen ions increases, the depth to which the hydrogenions enter the inside of the film increases. Therefore, by setting, inadvance, the thickness of the deposit DP to be formed in the step ST1according to the energy of ions to be supplied to the substrate W in thestep ST2, it is possible to suppress the ions from reaching the mask MKthrough the deposit DP in the step ST2.

Hereinafter, reference is made to FIG. 11. FIG. 11 is a viewschematically illustrating a processing system as an example which maybe used for executing the method illustrated in FIG. 1. In theembodiment, a plasma processing apparatus (hereinafter, referred to as“a first plasma processing apparatus 1 a”) used for executing the stepST1 and a plasma processing apparatus (hereinafter, referred to as “asecond plasma processing apparatus 1 b”) used for executing the step ST2may be different from each other. These plasma processing apparatusesmay be connected to each other via a vacuum transfer system. In order toexecute the method MT of this embodiment, the processing systemillustrated in FIG. 11 may be used.

A processing system PS illustrated in FIG. 11 includes stages 2 a to 2d, containers 4 a to 4 d, a loader module LM, an aligner AN, load-lockmodules LL1 and LL2, process modules PM1 to PM6, a transfer module TF,and a controller MC. In the processing system PS, each of the number ofstages, the number of containers, and the number of load-lock modulesmay be an arbitrary number equal to or greater than 2. The number ofprocess modules may be an arbitrary number equal to or greater than 2.

The stages 2 a to 2 d are arranged along one edge of the loader moduleLM. The containers 4 a to 4 d are mounted on the stages 2 a to 2 d,respectively. Each of the containers 4 a to 4 d is a container called,for example, a front opening unified pod (FOUP). Each of the containers4 a to 4 d is configured to accommodate the substrate W therein.

The loader module LM has a chamber. The pressure within the chamber ofthe loader module LM is set to atmospheric pressure. A transfer deviceTU1 is provided within the chamber of the loader module LM. The transferdevice TU1 is, for example, a multi-joint robot, and is controlled bythe controller MC. The transfer device TU1 is configured to transfer thesubstrate W between each of the containers 4 a to 4 d and the alignerAN, between the aligner AN and each of the load-lock modules LL1 andLL2, and between each of the load-lock modules LL1 and LL2 and each ofthe containers 4 a to 4 d. The aligner AN is connected to the loadermodule LM. The aligner AN is configured to adjust (position calibration)the position of the substrate W.

Each of the load-lock modules LL1 and LL2 is provided between the loadermodule LM and the transfer module TF. Each of the load-lock modules LL1and LL2 provides a preliminary decompression chamber.

The transfer module TF is connected to the load-lock modules LL1 and LL2via gate valves. The transfer module TF has a transfer chamber TC thatmay be decompressed. A transfer device TU2 is provided inside thetransfer chamber TC. The transfer device TU2 is, for example, amulti-joint robot, and is controlled by the controller MC. The transferdevice TU2 is configured to transfer the substrate W between each of theload-lock modules LL1 and LL2 and each of the process modules PM1 toPM6, and between any two process modules among the process modules PM1to PM6.

Each of the process modules PM1 to PM6 is a processing apparatus that isconfigured to perform a dedicated substrate processing. Among theprocess modules PM1 to PM6, one process module is the first plasmaprocessing apparatus 1 a. Among the process modules PM1 to PM6, anotherprocess module is the second plasma processing apparatus 1 b. In theexample illustrated in FIG. 11, the process module PM1 is the firstplasma processing apparatus 1 a, and the process module PM2 is thesecond plasma processing apparatus 1 b. In the embodiment, each of thefirst plasma processing apparatus 1 a and the second plasma processingapparatus 1 b may be the same plasma processing apparatus as the plasmaprocessing apparatus 1.

The above described transfer module TF constitutes a vacuum transfersystem. The transfer module TF is configured to transfer the substratebetween the first plasma processing apparatus 1 a and the second plasmaprocessing apparatus 1 b.

In the processing system PS, the controller MC is configured to controleach unit of the above processing system PS, for example, the firstplasma processing apparatus 1 a, the second plasma processing apparatus1 b, and the transfer module TF. The control for each unit of the firstplasma processing apparatus 1 a, by the controller MC, in execution ofthe step ST1 is the same as the above described control for each unit ofthe plasma processing apparatus 1, by the controller MC, in execution ofthe step ST1. The control for each unit of the second plasma processingapparatus 1 b, by the controller MC, in execution of the step ST2 is thesame as the above described control for each unit of the plasmaprocessing apparatus 1, by the controller MC, in execution of the stepST2.

After executing the step ST1, before executing the step ST2, thecontroller MC transfers the substrate W from the internal space 10 s ofthe chamber 10 of the first plasma processing apparatus 1 a to theinternal space 10 s of the chamber 10 of the second plasma processingapparatus 1 b through the pressure-reduced chamber of the transfermodule TF. For the transfer, the controller MC controls the transfermodule TF. That is, in the method MT, at least from the start time ofthe step ST1 to the end time of the step ST2, the substrate W is notexposed to the atmosphere. That is, at least from the start time of thestep ST1 to the end time of the step ST2, the substrate W is processedwithout breaking a vacuum in an environment where the substrate W isdisposed.

Various embodiments have been described above, but the presentdisclosure is not limited to the above described embodiments, andvarious omissions, substitutions and changes may be made. Also, it ispossible to form other embodiments by combining elements in differentembodiments.

For example, each of one or more plasma processing apparatuses used forexecuting the method MT may be any type of plasma processing apparatus.Such a plasma processing apparatus may be an inductively coupled plasmaprocessing apparatus or a plasma processing apparatus that uses surfacewaves such as microwaves in order to generate plasma. The first plasmaprocessing apparatus 1 a and the second plasma processing apparatus 1 bmay be different types of plasma processing apparatuses.

According to the embodiment, it is possible to suppress a film thicknessof the mask from being decreased due to etching of the film.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

What is claimed is:
 1. A method of etching comprising: providing asubstrate including a film and a mask on the film; selectively forming adeposit on a top surface of the mask; and etching the film after theforming of the deposit, wherein the etching of the film includes:forming, on the substrate, a layer of chemical species included inplasma from a processing gas, and supplying ions from an inert plasma tothe substrate, thereby causing the chemical species to react with thefilm.
 2. The method according to claim 1, wherein the film is asilicon-containing film, and the processing gas contains halogen andcarbon.
 3. A method of etching comprising: providing a substrateincluding a film and a mask on the film; selectively forming a depositon a top surface of the mask; and etching the film after the forming ofthe deposit, wherein the etching of the film includes modifying at leasta part of the film including an exposed surface by ions from plasma of afirst processing gas, thereby forming a modified region, and selectivelyetching the modified region by chemical species from plasma of a secondprocessing gas.
 4. The method according to claim 3, wherein the film ofthe substrate is a silicon nitride film, the first processing gascontains a hydrogen-containing gas, and the second processing gascontains a fluorine-containing gas and a hydrogen gas.
 5. The methodaccording to claim 3, wherein the film of the substrate is a siliconcarbide film, the first processing gas contains a nitrogen-containinggas, and the second processing gas contains a fluorine-containing gasand a hydrogen gas.
 6. The method according to claim 5, wherein athickness of the deposit is set such that the ions from the plasma ofthe first processing gas do not reach the mask through the deposit. 7.The method according to claim 6, wherein the forming of the deposit isperformed within a chamber, and the forming of the deposit includes:generating plasma from a mixed gas comprising a carbon-containing gasand an adjusting gas that adjusts an amount of the deposit within thechamber, and forming the deposit containing carbon on the top surface ofthe mask.
 8. The method according to claim 6, wherein the forming of thedeposit is performed within a chamber, and includes: supplying a mixedgas containing a silicon-containing gas and an adjusting gas thatadjusts an amount of the deposit into the chamber, supplying theadjusting gas into the chamber, repeating alternately the supplying ofthe mixed gas and the supplying of the adjusting gas, and supplying aradio-frequency power to generate plasma from the mixed gas within thechamber.
 9. The method according to claim 8, wherein the plasmaprocessing apparatus includes: a substrate holder including a lowerelectrode and configured to support the substrate within the chamber; anupper electrode provided above the substrate holder through a spacewithin the chamber; a first radio-frequency power supply electricallyconnected to the upper electrode and configured to generate a firstradio-frequency power; and a second radio-frequency power supplyelectrically connected to the lower electrode and configured to generatea second radio-frequency power having a frequency lower than a frequencyof the first radio-frequency power.
 10. The method according to claim 3,wherein a thickness of the deposit is set such that the ions from theplasma of the first processing gas do not reach the mask through thedeposit.
 11. The method according to claim 1, wherein the forming of thedeposit is performed within a chamber, and the forming of the depositincludes: generating plasma of a mixed gas containing acarbon-containing gas and an adjusting gas that adjusts an amount of thedeposit within the chamber to form the deposit on the top surface of themask.
 12. The method according to claim 1, wherein the forming of thedeposit is performed within a chamber, and includes: supplying a mixedgas containing a silicon-containing gas and an adjusting gas thatadjusts an amount of the deposit into the chamber, supplying theadjusting gas into the chamber, repeating alternately the supplying ofthe mixed gas and the supplying of the adjusting gas, and supplying aradio-frequency power to generate plasma from the mixed gas within thechamber.
 13. The method according to claim 11, wherein the plasmaprocessing apparatus comprises: a substrate holder including a lowerelectrode configured to support the substrate within the chamber; anupper electrode provided above the substrate holder through a spacewithin the chamber; a first radio-frequency power supply electricallyconnected to the upper electrode and configured to generate a firstradio-frequency power; and a second radio-frequency power supplyelectrically connected to the lower electrode configured to generate asecond radio-frequency power having a frequency lower than a frequencyof the first radio-frequency power.